The young wizard has chosen wisely. Making his Broadway debut in Thea Sharrock’s oddly arid revival of Peter Shaffer’s “Equus,” which opened Thursday night at the Broadhurst Theater, the 19-year-old film star Daniel Radcliffe steps into a mothball-preserved, off-the-rack part and wears it like a tailor’s delight  that is, a natural fit that allows room to stretch. Would that the production around him, first presented in London, showed off Mr. Shaffer’s 1973 psychodrama as flatteringly as it does its stage-virgin star.

Stretching without tearing is presumably what Mr. Radcliffe, who has spent most of his adolescence playing the schoolboy sorcerer in the globally popular Harry Potter movies, had in mind when he took on the role of Alan Strang, a 17-year-old suburban stableboy who commits grotesque and seemingly inexplicable crimes against horses.

For Alan Strang is, in a sense, a tidy inversion of Harry Potter. Both come of age in a menacing, magical world where the prospect of being devoured by darkness is always imminent. The difference is that for Harry that world is outside of him; Alan’s is of his own creation.

Like many beloved film actors Mr. Radcliffe has an air of heightened ordinariness, of the everyday lad who snags your attention with an extra, possibly dangerous gleam of intensity. That extra dimension has always been concentrated in Mr. Radcliffe’s Alsatian-blue gaze, very handy for glaring down otherworldly ghouls if you’re Harry Potter. Or if you’re Alan Strang, for blocking and enticing frightened grown-ups who both do and do not want to understand why you act as you do.

I had forgotten just how much is made of Alan’s eyes in “Equus,” which became a sensational upper-middlebrow hit when it opened in London and later on Broadway more than three decades ago. His stare is variously described as accusing, demanding and, in the case of a comely lass who just wants to bed him, amazing. Fortunately it projects as big from the stage as it does in cinematic close-up, as does Mr. Radcliffe’s compact, centered presence (which he retains even stark, raving naked). In any case, it’s the look of someone who sees and feels more deeply than ordinary folk. Such depth is to be envied  isn’t it?  even if it prohibits its possessors from fully belonging to human society.

That’s the conundrum at the heart of “Equus” and in most of Mr. Shaffer’s plays, particularly his “Amadeus,” in which an 18th-century wild child named Mozart has the lesser composer Salieri grinding his teeth in homicidal jealousy. In “Equus,” the envying is done by Martin Dysart (the superb Richard Griffiths), the psychiatrist asked to oversee Alan’s treatment after the boy blinds six horses one night in the stables where he works.

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From left, Daniel Radcliffe, Lorenzo Pisoni and Richard Griffiths in the Broadway revival of Peter Shaffers Equus.Credit...Sara Krulwich/The New York Times

Dysart acknowledges that what Alan has done is unspeakable. But as he shines a light into the recesses of the boy’s mind he sees the landscape of a self-made, chthonic religion in which the horse is God. For Dysart, a man in a sterile marriage who has measured out his life in patients’ files and annual holidays in Greece, Alan’s inner existence has the mythic grandeur of Homer’s Olympus.

Mr. Griffiths, who won a Tony as the inspiring, student-fondling teacher in Alan Bennett’s “History Boys,” plays Dysart with less masochistic swagger than I’ve ever seen. It was pretty hard to buy the kvetching of the sonorously suffering Richard Burton, who played the part in the 1977 film (and briefly on Broadway), about being so damned meek and ordinary.

On the other hand, Mr. Griffiths does banality beautifully, presenting Dysart in the early scenes as someone who has smoothed out every utterance to the same level of flat, professional detachment, lightly spiced with witty self-deprecation. He resists the temptation to play hotdog surfer, riding the purple waves of Mr. Shaffer’s symbol-saturated monologues. He builds Dysart’s character with care, so when the eruptions of naked doubt, self-contempt and sorrow finally break out, he’s earned them.

But while I can’t imagine another actor making more sense of Dysart, I’m not sure that the character  or for that matter, the play  benefits from such scrupulous treatment. Mr. Griffiths and Mr. Radcliffe (who stops short of the all-out religious ecstasy of Peter Firth, who created his part) are delivering utterly credible and often affecting performances. And I was always thoroughly engaged by their scenes together, which generate the genuine tension of clashing minds longing to meld.

The problem with such well-considered acting is that it throws a clear and merciless light on the hokum of the play as a whole. “Equus” was written in the shadow of the then voguish theories of R. D. Laing, which championed the creative beauty within madness while fixing blame on the repressiveness of the conventional family.

We were just out of the 1960s when “Equus” arrived, and this creed of communing with one’s inner madman had more appeal than it does today, when people are doing their best to hold themselves together as familiar social structures threaten collapse. To buy into the innate worth of Alan’s raging fantasies, we more than ever have to feel viscerally the exhilaration he feels.

Yet for all the inventive stagecraft of John Napier, the designer of this and the first production, and Ms. Sharrock (who stays close to the spirit of John Dexter’s original direction)  for all the prancing horse-masked dancers on the revolving stage with its Stonehenge-like blocks  I never felt a ripple of vicarious passion. The careful realism of Mr. Griffiths’s and Mr. Radcliffe’s performances makes you appraise their characters with a newly sober eye.

This means that the homoerotic aspect of Alan’s equine dreams becomes excruciatingly blatant, a garden-variety sexual identity crisis dressed up for a night at the races. You can hear every metaphor falling into place with an amplified click, just as the psychological clues to the detective-story aspect of the play seem to be announced with the equivalent of a suddenly illuminated light bulb.

It doesn’t help that Ms. Sharrock has the supporting cast members turning directly to the audience to make such announcements (things along the lines of, “Well, now that you mention it, he did keep this strange picture above his bed.”). These performances are infected with the let’s-out-British-the-British strain that often happens to New York actors mixed with English actors in English plays.

Such affectations would matter less if everyone were pitched at the same stylistic tone. But as Alan’s child-warping parents, Carolyn McCormick and T. Ryder Smith offer broad emotions without the refining detail of individual character. Anna Camp is appealingly natural as the young woman who unwittingly leads Alan to his acts of destruction.

But Kate Mulgrew, as the magistrate who is Dysart’s confidante, is alternately as plummy and mannered as a society matron in a Maugham drawing-room comedy and as portentous as a sinister housekeeper in a creaky-old-house chiller.

Ms. Mulgrew, for the record, was the only cast member awarded with exit applause before the final curtain when I saw the show (this after a particularly flamboyant declaration to Dysart). Personally, I winced whenever she opened her mouth, but I think the audience was hungry for the sort of campy grandeur she provided.

There’s no question that “Equus” has dated, particularly in its presentation of psychiatric investigations (something Mr. Shaffer humbly admits in a program note). But taking it too seriously may not be the best way to serve it in revival. This version had no crackling artificial fire to match the annoying smoke that kept rising through the stage floor. And as much as I admired the sensitivity and intelligence of Mr. Griffiths’s and Mr. Radcliffe’s performances, this revival might have been better off if everyone had just gone for the Gothic.